copies-rust: remove an unnecessary format!() inside assert!()...
copies-rust: remove an unnecessary format!() inside assert!()
The `assert!()` macro supports formatting. Rust 2021 no longer
supports an unnecessary `format!()` inside it. I noticed because I
recently update my Rust toolchain and `test-check-cargo-lock.t`
started failing.
Differential Revision:
https://phab.mercurial-scm.org/D10085